一种无镍磷化剂的研制

Development of a Nickel-Free Phosphating Agent

镍离子对人体和环保都不利,迫切需要研制一种无镍磷化工艺。将硝酸镁、硝酸钴和钨酸钠复配替代原磷化液中的硝酸镍,并加入钨酸钠,以提高磷化膜的耐蚀性。通过正交试验确定最优磷化液配方。结果表明:磷化膜外观均匀、致密,磷化膜结晶状态为针状,结晶颗粒尺寸在2～4μm之间,P比和面比均达到标准要求;磷化膜耐碱性试验失重比在标准范围内;漆膜附着力试验(冲击、杯突、弯曲、方格、铅笔硬度等试验)均符合100/100的标准;漆膜盐雾试验达到720h以上、单侧腐蚀2mm以下的标准;镀锌板漆膜耐水二次密着性达到标准要求,完全可以替代现有含镍磷化剂。

Since nickel ions are harmful to human health and environment,it is imperative to develop nickel-free phosphating process for replacing current phosphating process. Thus magnesium nitrate,cobalt nitrate and sodium tungstate were used to replace nickel nitrate in original formulation so as to improve the corrosion resistance of the phosphating coating. The optimal composition of the phosphating solution was determined by making use of orthogonal tests. It was found that the phosphating coating made from the title phosphating agent was uniform and compact and consisted of needle-like grains with a size of 2～4 μm. Besides,the resistance to alkali and weight loss ratio of the phosphating coating were within specified ranges,and its adhesion force (determined by impacting,cupping,bending grid and pencil hardness test) followed the 100/100 standard. Moreover,the phosphating coating had a salt-spraying anticorrosion life of over 720 h,with single edge corrosion thickness to be below 2 mm. At the same time,the Ni-free phosphating coating on galvanized steel sheets possessed acceptable resistance to water and second-time adhesion as well,and it could be well used to replace currently used Ni-containing phosphating coating.